Filter element and methods of manufacturing and using same

ABSTRACT

A coreless and spirally wound non-woven filter element is provided. The filter element includes at least one band of base media having a selected porosity and an interlay having a different porosity within at least one band of base media. The presence of the interlay in the filter element can create additional surface area within the contiguous construction of a filter element for filtration. This interlay can also create the ability to change direction of flow and to increase the deposition of specifically sized contaminants.

RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No.13/278,689, filed Oct. 21, 2011, which is a divisional of U.S.application Ser. No. 11/607,364, filed Dec. 1, 2006, now U.S. Pat. No.8,062,523 issued on Nov. 22, 2011, the content of all of which is herebyincorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to filter elements and methods used intheir manufacture.

BACKGROUND ART

There are machines used to manufacture tubular filter elements in acontinuous process. U.S. Pat. No. 4,101,423 discloses a tubular filterelement made on a single-stage multiple winding machine of helicallywound and overlapping layers such as an inner layer of high wetstrength, highly porous paper, a second layer of thin microporousfiltration material of a sterilizing grade and an outer layer of aporous sheet of expanded polyethylene and an outer porous layer tosupport the filtration material. The layers are wrapped on a fixedmandrel to be self-overlapping in a single layer overlap and advance inunison along the mandrel as they are wrapped so that there is norelative motion between the adjacent layers of the laminate. An adhesivematerial that blocks the passage of the particulate matter and bacteriabeing filtered seals the second filtration layer in the region ofoverlap. The ends of the tubular laminate construction are impregnatedover a predetermined length adjacent to each edge of the constructionwith a suitable sealing adhesive material such as a polyurethane pottingcompound. When the adhesive material cures, the end portions providemechanical support for the tube while blocking the passage of the fluidor the particulate and bacterial contaminants. (See Col. 5, Ins. 4-26.)

A circularly wound spiraled chromatographic column is shown in U.S. Pat.No. 4,986,909. Here, a sandwich or laminate of alternating layers ofswellable fibrous matrix in sheet form and layers of spacer means, withthe periphery of the sandwich is compressed into a fluid-tightconfiguration. Typically, the peripheral edges of alternating discs ofswellable fibrous matrix and spacer means are joined. Preferably, thefibrous matrix contains or has bonded therein a thermoplastic polymericmaterial, as does the spacer means. The edges may be joined byappropriate heating, e.g. sonic welding. (See Col. 10, Ins. 40-61.)

Another spirally, circularly wound filter element is disclosed in U.S.Pat. No. 5,114,582 and comprises one or more filter elements spirallywound on a cylindrical permeate transport tube. Each filter elementcomprises a heat-sealed membrane element and a feed spacer. (SeeAbstract.)

A process for the manufacture of porous tubes of high permeability madefrom a carbon-carbon composite material in a strip of mat spirally woundon a mandrel is disclosed in U.S. Pat. No. 5,264,162. Porous tubes aremade from said material by winding over a mandrel a nonwoven sheet, madefrom a carbon fiber precursor, followed by compression and hotstabilization of the assembly. The sheet is impregnated by a resin,followed by a thermal carbonization treatment of the resin. Tubes areobtained having a high permeability, small pore diameter and an innersurface of low rugosity. (See Abstract.) Also disclosed is the use ofsuccessive mat layers, making it possible to obtain, in the final tube,pore diameters which increase in the direction of the flux to befiltered, generally from the inside towards the outside of the tube. Itis advantageous that these pore diameters are substantially in a ratioof 10 between one layer and the next, which may be obtained by adjustingthe density of the mat and/or the diameter of the fibers. (See Col. 4,Ins. 10-20.)

A helically wound, single wrap filter element is disclosed in U.S. Pat.No. 5,409,515, including a porous membrane of a polytetrafluoroethyleneand one or more sheets composed of fibers made of a thermally meltingsynthetic resin. (See Abstract.) The sheets are thermally fused over aselected length. (See Col. Ins. 40-46.)

SUMMARY OF THE INVENTION

It is the general object of the invention to provide an improved filterelement made with improved methods and machines for their manufacture.

This object is achieved with a filter element made of at least onenonwoven fabric of a homogeneous mixture of a base and a binder materialthat is compressed to form a mat or sheet of selected porosity. Thebinder fiber has at least a surface with a melting temperature lowerthan that of the base fiber. The sheet is formed into a selectedgeometric shape and heated to thermally fused to bind the base fiberinto a porous filter element. The preferred shape is a helically woundtube of plural sheets, each sheet being self-overlapped and compressedto overlap another sheet. Each sheet preferably heated and compressedindividually and the sheets may be selected to have different porositiesand densities. The binder material is selected from the group consistingof thermoplastic and resin, and the base material is selected from thegroup consisting of thermoplastic and natural.

The machinery preferably used to produce the filter element employs thea method of manufacture that includes the step of forming a nonwovenfabric of a homogeneous web of a base fiber and a binder fiber, asexplained above, compressed to form a sheet of selected porosity. Pluralsheets of nonwoven fabric are wrapped helically on a multi-stationwrapping machine with individual belts, each powered by a capstan toform individual layers that overlap to form a laminate. The tension ofeach belt is selected to compress each layer a selected degree. Eachlayer is heated to accomplish the thermal fusion step. Cooling fluid ispumped through the hollow mandrel to prevent excessive heat build-up inthe mandrel. The machine is controlled by a computer, which receivesinput signals that adjust machine functions such as the capstan drivingmotor speed, the tensions of the sheet wrapping belts, the temperatureof the heater array used to accomplish thermal fusion of each layer, andthe flow of cooling fluid flowing through the hollow mandrel.

The above as well as additional objects, features, and advantages of theinvention will become apparent in the following detailed description.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view in partial section of the preferredembodiment of the invention that illustrates a multi-overlapped corelessfilter element made in a four station wrapping machine using four rollsof selected nonwoven fabric.

FIG. 2 is a cross-sectional view that illustrates the multi-overlappedcoreless filter element of FIG. 1 being formed on a hollow mandrel.

FIG. 3 is a schematic top view of three stations of the machine used tomanufacture the filter element of FIG. 1.

FIG. 4 is a perspective view that illustrates the preferred embodimentof a multi-stage winding machine used to that produce the filter elementof FIG. 1.

FIG. 5 is a block diagram of the preferred nonwoven fabric manufacturingprocess used to produce the filter element of FIG. 1.

FIG. 6A illustrate a cross-sectional view of a multi-overlapped corelessfilter element having an interlaying band in accordance with anotherembodiment of the present invention.

FIG. 6B illustrates a strip for forming an interlaying band positionedagainst a surface of a strip for forming a band of the filter elementfor simultaneous winding to provide the configuration shown in FIG. 6A.

FIG. 7 illustrates a cross-section view of another multi-overlappedcoreless filter element having an interleafing band in accordance withone embodiment of the present invention.

FIG. 8 illustrates a cross-section view of a multi-overlapped corelessfilter element having another interleafing band in accordance withanother embodiment of the present invention

DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring to FIG. 1 of the drawings, the numeral 11 designates amulti-overlapped coreless filter element constructed according to theprinciples of the invention. It includes a first multi-overlappednonwoven fabric strip 13, a second multi-overlapped nonwoven fabricstrip 15, a third multi-overlapped nonwoven fabric strip 17, and afourth multi-overlapped nonwoven fabric strip 19. Each fabric strip 13,15, 17, 19 is spirally or helically wound in overlapping layers to formoverlapping bands 14, 16, 18, 20, respectively. The radially interiorsurface 21 of band 14 forms the periphery of an axially extendingannular space (i.e., pathway) that extends from one end 25 of the filterelement to the oppositely facing end 27 of the filter element 11. In thedrawings the thickness of the fabric is exaggerated.

In FIG. 2 of the drawings, the numeral 47 designates a hollowcylindrical mandrel with an annular exterior surface 49 and an annularinterior surface 51, said annular interior surface 51 forming theperiphery of a cylindrical channel 53, through which flows a liquid orgas heat exchange medium (not shown). Band 14 of multi-overlappednonwoven fabric strip 13, is shown overlapped by band 16 ofmulti-overlapped non-woven fabric strip 15, which in turn is overlappedby band 18 of multi-overlapped nonwoven fabric strip 17, which is thenoverlapped by band 20 of multi-overlapped nonwoven fabric strip 19.

As shown in FIG. 3 of the drawings, only three stages are shown of themulti-stage winding machine shown in greater detail in FIG. 4. In FIG.3, a first compression belt 55 is shown wrapping, in a multi-overlappedfashion, nonwoven fabric strip 13 about the hollow mandrel 47. A secondcompression belt 57 is shown wrapping, in a multi-overlapped fashion,nonwoven fabric strip 15 about multi-overlapped nonwoven fabric strip13. A third compression belt 59 is shown wrapping, in a multi-overlappedfashion, non-woven fabric strip 17 about multi-overlapped nonwovenfabric strip 15. A first heater array of preferably infrared heaters 63is shown in a position to apply heat, simultaneously with thecompression of compression belt 55, to multi-overlapped nonwoven fabricstrip 13. A second heater array of infrared heaters 65 is shown in aposition to apply heat, simultaneously with the compression ofcompression belt 57, to multi-overlapped nonwoven fabric strip 15. Athird heater array of infrared heaters 67 is shown in a position toapply heat, simultaneously with the compression of compression belt 59,to multi-overlapped nonwoven fabric strip 17.

Referring now to FIG. 4 of the drawings, numeral 71 designates amulti-stage winding machine for manufacturing multi-overlapped corelessfilter elements 11. A roll of nonwoven fabric strip 13 is shown mountedon a roll support 75 consisting of an upright member 77 onto which aremounted one or more cylindrical roll support shafts 79 extendingperpendicularly outward from the upright member 77 to receive thetubular core (not shown) of the roll of non-woven fabric strip 13. Eachroll support shaft 79 is connected to the upright member 77 at a pointalong the length of the upright member 77. The upright member 77 isconnected at its base to a plurality of horizontal legs (not shown)which extend perpendicularly outward to such length as to providesupport for the upright member 77, each roll support shaft 79, and eachroll non-woven the fabric strip 13 loaded onto each roll support shaft79.

A feed tray 81 consists of a rectangular plate with its two longestopposing edges 83 and 85 each turned up at a right angle so as to form achannel which supports and guides and is adjustable to the width of thenonwoven fabric strip 13. Each stage of the winding machine 71 has afeed tray 81 and a tensioner roller 147 connected to an air cylinder(not shown).

Heater array support 87, a mounting plate for the first heater array 63,stands vertically in a plane which is perpendicular to the axis 89 ofthe winding machine 71. The heater array support 87 is connected alongits base edge to a machine support structure 91 which extends parallelto the axis 89 of the winding machine 71 and supports each stagethereof. The heater array support 87 has an input surface (not shown)and an output surface 93. Connected to the output surface 93 andextending along the axis 89 and through each stage of the windingmachine 71 is a hollow mandrel 47. Attached to the input surface of theheater array support 87 is a conduit (not shown) for transporting theheat exchange medium from a pumping device (represented schematically inFIG. 7, numeral 324) to the heater array support 87, through an aperture(not shown) in the heater array support 87, and into the cylindricalchannel 53 (see FIG. 2) of the hollow mandrel 47. Connected to theoutput surface 93 of the heater array support 87 is a plurality ofheater actuators 97 each of which consists of a dial adjustmentmechanism 99 connected through a gear mechanism (not shown) to a heateractuator plate 101.

Attached to each heater actuator plate 101 and extending outward fromthe output surface 93 of the heater array support 87 and parallel to theaxis 89 of the winding machine 71 is an infrared heater 63. Eachinfrared heater 63 is attached to a corresponding heater actuator plate101 in such a fashion as to direct the heat perpendicular to and in thedirection of the hollow mandrel 47. Each infrared heater 63 extendsoutward from the output surface 93 of the heater array support 87 aselected distance.

A pair of capstans consisting of a driving capstan 105 and a drivencapstan 106 stand vertically with their axes (not shown) perpendicularto and on either side of the axis 89 of the winding machine 71. Thedriving capstan 105 is mounted onto a driving capstan gearbox 107 andthe driven capstan 106 is mounted onto a driven capstan gearbox 109. Thedriving capstan gearbox 107 is connected at its base to a gearboxplatform 113. The gearbox platform 113 is a rectangular plate that sitsatop the machine support structure 91 in a horizontal plane. A capstandriving motor (not shown) is mounted underneath the gearbox platform 113and has a shaft (not shown) which extends through an aperture (notshown) in the gearbox platform 113 and connects to the gears of thedriving capstan gearbox 107. The driving capstan gearbox 107 isconnected to the driven capstan gearbox 109 by a splined shaft (notshown in the first-stage, but identical to the splined shaft 111 of thefourth stage) thereby providing a means for driving the capstans 105 and106 at the same angular speed but in opposing directions.

The driven capstan gearbox 109 is connected at its base to a gearboxsliding plate 115. The underside of the gearbox sliding plate 115 has aplurality of grooves that extend along its length and parallel to thelength of the gearbox platform 113. The grooves of the gearbox slidingplate 115 receive the rails of a digital linear encoder 117 therebyallowing the digital linear encoders 117 to incrementally measure thelocation of the driven capstan 109 along the rails of the digital linearencoder 117 relative to a reference point on the digital linear encoder117. The digital linear encoder 117 can be of the type disclosed in U.S.Pat. No. 4,586,760 or any other incremental linear measuring deviceknown to persons skilled in the art. Near the center of the gearboxplatform 113 and cut through the thickness of the platform is anarc-shaped slot (not shown in the first-stage, but identical to thearc-shaped slot 119 of the fourth stage), the chord of which is parallelto the length of the gearbox platform 113. A gearbox platform adjustmentset screw (not shown in the first stage, but identical to the gearboxplatform adjustment set screw 121 of the fourth stage) passes throughthe arc-shaped slot identical to slot 119 and is received into athreaded aperture (not shown) in the machine support structure 91. Theangle of the belt 55 relative to the mandrel 47 may be adjusted withthis mechanism.

Capstan sleeves 123 and 125 are concentric about the axes of the drivingcapstan 105 and the driven capstan 106, respectively. The radiallyinterior surfaces of the capstan sleeves 123 and 125 are mated with theradially exterior surfaces of the driving capstan 105 and the drivencapstan 106, respectively, and are attached thereto by suitable means ata selected location on the driving capstan 105 and on the driven capstan106. Annular capstan sleeve flanges 127 and 129 extend radially outwardfrom the driving capstan 105 and the driven capstan 106, respectively.

Compression belt 55 forms a closed loop around one half of the peripheryof the driving capstan 105 and one half of the periphery of the drivencapstan 106 and is placed in tension by the distance between the axes ofthe driving capstan 105 and the driven capstan 106. The compression beltcrosses over itself a single time between the driving capstan 105 andthe driven capstan 106. In addition, the compression belt 55 forms asingle spiral around the hollow mandrel 47.

A tensioner air cylinder 133 is mounted onto the gearbox platform 113 atthe same end as the driven capstan gearbox 109. The tensioner aircylinder 133 is a commonly used pneumatic cylinder with a shaft 135 thatextends from one end of the tensioner air cylinder 133 in parallel withthe length of the gearbox platform 113 and is connected at the opposingend to the driven capstan gearbox 109.

Three additional stages of the multi-stage winding machine 71 are shownin FIG. 4. Each such additional stage consists of identical componentsas the first stage with the exception that the heater array support 137of each additional stage includes an aperture 139 concentric about theaxis 89 of the winding machine 71 through which the hollow mandrel 47passes with sufficient clearance for bands 14, 16, 18, 20 of the filterelement 11; and with the exception that the feed tray 81 is replaced bya feed tensioner 141 consisting of a vertically upright member 143connected at its base to a plurality of horizontal legs 145 andconnected at the opposite end to feed tensioner rollers 147.

Referring now to FIG. 5 of the drawings, a block diagram of each step ofthe manufacturing process of the nonwoven fabric is illustrated. Eachsignificant step of the manufacturing process is depicted in a separateblock. In block 151, step 1 is the acquisition of fiber, usually in theform of a bale purchased from a textile fiber producer. Each strip 13,15, 17, 19 is composed of one or more fibers. If a strip 13, 15, 17, 19is composed of only one fiber, it should be of the type which consistsof a lower melting point outer shell and a higher melting point innercore. If a strip 13, 15, 17 19 is composed of two or more fibers, atleast one of the fibers must have a lower melting point than the othersor be of the shell and core type mentioned above.

In block 153, step 2 is opening and weighing of the fiber materials. Thefibers are transported to a synchro-blender where they are furtheropened in preparation for final blending in block 155.

In block 155, step 3 is the final blending of the fibers whereby theindividual fibers are thoroughly intermixed by a series of cylindricalrollers and lickerins to provide a homogeneous dispersion of fibers.This step is performed in a blender similar to the blender disclosed inU.S. Pat. No. 3,744,092.

In block 157, step 4 is the transportation of the thoroughly mixedfibers via an air duct system consisting of a duct approximately 12inches in diameter through which air is circulated at a rate ofapproximately 1,500 feet per minute from the blender to the feeder.

In block 159, step 5 is the feeding of the intermixed fibers into afeeder similar to the feeder disclosed in U.S. Pat. Nos. 2,774,294 and2,890,497.

Block 161, step 6 is a web formation step in which the fibers areconveyed from the feeder to a webber similar to the webber disclosed inU.S. Pat. Nos. 2,890,497 and 2,703,441, consisting of a plurality ofcylindrical rollers and a lickerin such that a continuous web of thehomogeneously dispersed fibers is formed.

Block 163, step 7 is a liquefaction and compression step carried out ina series of air-draft ovens and/or alternative heat sources in which aflow of air heated to a selected temperature is blown down onto the webthereby causing liquefaction of all or part of particular types of thehomogeneously dispersed fibers as more fully explained hereinafter.Simultaneously with the liquefaction of all or part of particular typesof the homogeneously dispersed fibers, is compression of thecontinuously formed web into a thin sheet. The air in the air-draftovens is saturated to near 100% with low pressure steam. Liquid water ispumped through pipes into the air-draft ovens where it spilled ontoheated stainless steel plates thereby creating low pressure steam. Thesaturation level required is dependent upon the temperature inside theair-draft ovens which ranges from 200 degrees to 550 degrees Fahrenheit.The steam neutralizes the static electricity created by the air which isrecirculated at rates of up to 40,000 cubic feet per minute. There is apressure differential across the web in the air-draft oven of between 4and 8 inches of water column. Residence time for the web in theair-draft ovens is dependent upon and coordinated with the dischargerate of the web being produced at the webber.

In block 165, step 8 is the compression of the sheet of homogeneouslydispersed fibers into a nonwoven fabric with a thickness required forthe desired filtration efficiency by conveying the sheet between twocylindrical stainless steel rollers.

In block 166, step 8-A, is the formation of a roller of the nonwovenfabric on a winder.

In block 167, step 9 of the manufacturing process is the formation ofstrips from the sheet of nonwoven fabric. Cutting devices are positionedat selected spots across the width of the sheet of nonwoven fabric so asto cut the sheet into a plurality of strips of selected widths therebyforming strips of nonwoven fabric such as 13, 15, 17, 19.

In block 169, step 10 the nonwoven strips 13, 15, 17, 19 are wound ontocores which are in the form of cylindrical tubes on a commonly knownwinder consisting of a plurality of cylindrical rollers for aligning andwinding the strips of nonwoven fabric 13, 15, 17, 19 onto cores.

The entire nonwoven sheet manufacturing process takes place in ahumidity-controlled environment. The relative humidity of the air in theenvironment ranges from 60% to 80% as measured by wet bulb/dry bulbthermometer and an enthalpy chart.

Each non-woven fabric strip 13, 15, 17, 19, is composed of selectedpolymeric fibers such as polyester and polypropylene which serve as bothbase fibers and binder fibers. Base fibers have higher melting pointsthan binder fibers. The role of base fibers is to produce small porestructures in the coreless filter element 11. The role of the binderfiber or binder material is to bond the base fibers into a rigid filterelement that does not require a separate core. The binder fibers mayconsist of a pure fiber or of one having a lower melting point outershell and a higher melting point inner core. If the binder fiber is ofthe pure type, then it will liquefy throughout in the presence ofsufficient heat. If the binder fiber has an outer shell and an innercore, then it is subjected to temperatures that liquefy only the outershell in the presence of heat, leaving the inner core to assist the basefiber in producing small pore structures. The role therefor of thebinder fiber is to liquefy either in whole or in part in the presence ofheat, the liquid fraction thereof to wick onto the base fibers to form abond point between the base fibers, thereby bonding the base fiberstogether upon cooling. The binder material may be in a form other thanfibrous.

Referring now to a preferred embodiment of the invention, the basefibers and binder fibers are blended according to the manufacturingprocess set forth in FIG. 5 to form rolls of non-woven fabric strips 13,15, 17, 19, each of a selected composition. Upon completion of themanufacture of rolls of nonwoven fabric strips 13, 15, 17, 19, the rollsthereof are loaded onto the roll support shafts 79 of the roll support75 at each stage of the winding machine 71. Each roll support 75 ispositioned to introduce the non-woven fabric strips 13, 15, 17, 19, at aselected angle to the hollow mandrel 47. The desired specifications fora multi-overlapped coreless filter element 11 are then selected in themanner set forth in U.S. Pat. No. 5,827,430, which is herebyincorporated herein by reference.

A length of the non-woven fabric strip 13 is unrolled and fed over thefeed tray 81 such that it lies between the upturned edges 83 and 85 ofthe feed tray 81. The feed tray 81 is positioned such that the non-wovenfabric strip 13 is introduced to the hollow mandrel 47 at a selectedangle, and the driving capstan gearbox 107 thereafter acts to turn thedriving capstan 105. The splined shaft of the first stage of the windingmachine 71 transmits power to the driven capstan gearbox 109, the gearsof which turn the driven capstan 106 at the same angular speed but inthe opposite direction as the driving capstan 105. Friction between theinterior surface of the compression belt 55 and the radially exteriorsurfaces of the driving capstan 105 and the driven capstan 106 allowsthe belt to turn with the capstans 105 and 106 without tangentialslippage. The capstan sleeve flanges 127 and 129 of the capstan sleeves123 and 125, respectively, prohibit the compression belt 55 fromdownward slippage on the driving and driven capstans 105 and 106,respectively.

The leading edge 31 of the non-woven fabric strip 13 is then fed betweenthe annular exterior surface 49 of the hollow mandrel 47 and thecompression belt 55 at the point where the compression belt 55 makes itssingle spiral loop around the hollow mandrel 47. Because the frictiondrag generated between the compression belt 55 and the non-woven fabricstrip 13 is greater than the friction drag generated between thenon-woven fabric strip 13 and the hollow mandrel 47, the coreless filterelement 11 is formed in a conical helix shape and is driven along thehollow mandrel 47 toward the free end thereof. The feed angle betweenthe non-woven fabric strip 13 and the hollow mandrel 47 is such that thenon-woven fabric strip 13 overlaps itself a plurality of times as it iscompressed between the compression belt 55 and the hollow mandrel 47producing the multi-overlapped conical helix feature of the presentinvention. The source of the selected compressive force of thecompression belt 55 is the tension in the compression belt 55 which isdetermined by the selected distance between the axes of the drivingcapstan 105 and the driven capstan 106. Since the driven capstan 106 isconnected to the driven capstan gearbox 109 which is connected at itsbase to the gearbox sliding plate 115, the driven capstan 106 is free totranslate along the rails of the digital linear encoder 117. The digitallinear encoder 117 incrementally measures the location of the drivencapstan gearbox 109 along the rails of the digital linear encoder 117relative to a reference point on the digital linear encoder 117. Thecompressive force delivered by compression belt 55 to the nonwovenfabric strip 13 is controlled and maintained by a selected pressure inthe pneumatic tensioner air cylinder 133, the shaft 135 of which isconnected to the base of the driven capstan gearbox 109. The pressure inthe pneumatic tensioner air cylinder 133 is adjusted according tooperational inputs such that its shaft 135 is either extended orretracted thereby controlling and maintaining the compressive forcedelivered by compression belt 55 to the nonwoven fabric strip 13.

Applied simultaneously with the aforementioned compression to themulti-overlapped non-woven fabric strip 13 is a selected amount of heatgenerated by an array infrared heaters 63 located a selected distancefrom the non-woven fabric strip 13. Each infrared heater 63 is connectedto a heater actuator plate 101 which provides for movement of eachinfrared heater 63 toward or away from the hollow mandrel 47. The dialadjustment mechanism 99 of the heater actuator plate 101 allows forincremental adjustment of the distance between each infrared heater 63and the hollow mandrel 47. Each infrared heater 63 acts to heat themulti-overlapped non-woven fabric strip 13 to a selected temperaturesuch that the base fibers of the multi-overlapped non-woven fabric strip13 are bonded together both within the strip and between themulti-overlapped layers of band 14 by the wicking process of theliquefied binder fibers.

As the non-woven fabric strip 13 is simultaneously heated and compressedto produce the desired porosity, a heat exchange medium is pumpedthrough the cylindrical channel 53 of the hollow mandrel 47 by a pumpingdevice (not shown) at a selected flow rate for the purpose ofmaintaining a selected temperature on the exterior surface 49 of thehollow mandrel 47. One or more temperature detecting devices such asthermocouples (not shown) are in communication with the heat exchangemedium for the purpose of detecting the temperature of the heat exchangemedium.

The non-woven fabric strip 13 continues to be overlapped upon itselfthereby forming band 14 which is driven along the hollow mandrel 47through the apertures 139 of the heater array supports 137 of eachremaining stage of the winding machine 71 in a continuous unendingfashion. Once band 14 has passed through all stages of the windingmachine 71 a length of the second-stage non-woven fabric strip 15 isunrolled and fed between the feed tensioner rollers 147 of a feedtensioner 141. The leading edge 35 of the non-woven fabric strip 15 isthen fed between the compression belt 57 and the annular exteriorsurface of band 14 at the point where the compression belt 57 makes itssingle spiral around the hollow mandrel 47.

The nonwoven fabric strip 15 is simultaneously compressed and heated byidentical means as the first-stage nonwoven fabric strip 13. Thenon-woven fabric strip 15 continues to be overlapped upon itself,thereby forming band 16, the annular interior surface of which is bondedto the annular exterior surface of band 14. The combined bands 14 and 16are driven along the hollow mandrel 47 through the apertures 139 of theheater array supports 137 of each remaining stage of the winding machine71 in a continuously unending fashion. Once the combined bands 14 and 16have passed through all remaining stages of the winding machine 71 alength of the third-stage non-woven fabric strip 17 is unrolled and fedbetween the feed tensioner rollers 147 of a feed tensioner 141. Theleading edge 39 of the non-woven fabric strip 17 is then fed between thecompression belt 59 and the annular exterior surface of band 16 at thepoint where the compression belt 59 makes its single spiral around thehollow mandrel 47.

The nonwoven fabric strip 17 is simultaneously compressed and heated byidentical means as the first-stage nonwoven fabric strip 13. Thenon-woven fabric strip 17 continues to be overlapped upon itself,thereby forming band 18, the annular interior surface of which is bondedto the annular exterior surface of band 16. The combined bands 14, 16,18 are driven along the hollow mandrel 47 through the apertures 139 ofthe heater array supports 137 of each remaining stage of the windingmachine 71 in a continuously unending fashion. Once the combined bands14, 16, 18 have passed through all remaining stages of the windingmachine 71 a length of the fourth-stage non-woven fabric strip 19 isunrolled and fed between the feed tensioner rollers 147 of a feedtensioner 141. The leading edge 43 of the non-woven fabric strip 19 isthen fed between the compression belt 61 and the annular exteriorsurface of band 18 at the point where the compression belt 61 makes itssingle spiral around the hollow mandrel 47.

The non-woven fabric strip 19 continues to be overlapped upon itself,thereby forming band 20, the annular interior surface of which is bondedto the annular exterior surface of band 18. The combined bands 14, 16,18, 20 are driven along the hollow mandrel 47 in a continuously unendingfashion toward a measuring device (not shown) and a cutting device (notshown). Once the combined bands 14, 16, 18, and 20 have passed throughthe final stage of the winding machine 71, the filter element 11 ismeasured by the measuring device and cut to length by the cuttingdevice.

The angular speed of the capstan driving motor is such that thenon-woven fabric strips 13, 15, 17, 19 remain in close enough proximityto the infrared heaters 63, 65, 67, 68 for a selected duration of timeso as to allow proper liquefaction of the binder fibers. Also,sufficient distance between stages is provided so that the binder fibersare allowed to partially cool thereby bonding the base fibers withineach nonwoven strip 13, 15, 17, 19, between each layer thereof, andbetween each band 14, 16, 18, 20, providing the desired porosity betweeneach layer and between each band 14, 16, 18, 20.

The simultaneous application of selected amounts of heat and compressionto the layers of non-woven fabric strips 13, 15, 17, 19, is such thatonly selected properties are altered resulting in a coreless filterelement 11 with sufficient structural strength to be self-supporting,i.e., requiring no structural core, while maintaining the desiredporosity.

The simultaneous application of selected amounts of heat and compressionto the non-woven fabric strips 13, 15, 17, 19, as described above, allowfor systematic variation of the density of the layers of non-wovenfabric strips 13, 15, 17, 19, across the wall of the filter element andthe systematic variation of the porosity of the base fibers, of theelement 11.

The direction of flow of filtrate through the filter element 11 can beeither from the core toward the annular outside wall or from the annularoutside wall toward the core, but in either case the filtrate flow isgenerally perpendicular to the axis of the filter element 11. However,due to the conical helix nature of the layers of non-woven fabric strips13, 15, 17, 19, the pores formed by the bonded base fibers lie at anangle to the axis of the filter element 11 making it more difficult forlarge particles of filtrate to pass through the filter element 11.

The filter element 11 may be finished by capping the ends 25 and 27 byany suitable means known to persons skilled in the art, such as pottingin a polymeric resin.

A cable-activated kill switch (not shown) extends over the length of thewinding machine 71 for the purpose of halting the winding machine 71.

An example of the method and means of manufacturing a filter element ofthe type shown in FIG. 1 is as follows: Four different types of fiberswere purchased from Hoechst Celanese of Charlotte, N.C., sold under thefiber designation “252,” “121,” “224,” and “271”. Fiber “252” was of thecore and shell type, whereas fibers “121,” “224,” and “271” were of thesingle component pure type. The denier of fiber “252” was 3 and itslength was 1.500 inches. The denier of fiber “121” was 1 and its lengthwas 1.500 inches. The denier of fiber “224” was 6 and its length was2.000 inches. The denier of fiber “271” was 15 and its length was 3.000inches. A first blend of fibers was manufactured from fiber “121” andfiber “252” composed of 50% by weight of each fiber type. A second blendof fibers was manufactured from fiber “224” and fiber “252” composed of50% by weight of each fiber type. A third blend of fibers wasmanufactured with a composition of 25% by weight of fiber “121” and 25%by weight of fiber “224” and 50% by weight of fiber “252”. A fourthblend of fibers was manufactured from fiber “271” and fiber “252”composed of 50% by weight of each fiber type. Fiber “252” being of thecore and shell type served as the binder fiber in each of theaforementioned blends. Each blend of fibers was manufactured accordingto the process set forth in FIG. 5. Each blend of fibers was formed intoa web which was approximately ½ inch in thickness. The thickness of eachweb was reduced by approximately 50% forming a mat during its residencetime of ninety seconds in the air draft ovens due to the recirculationof steam-saturated air at approximately 40,000 cubic feet per minute ata temperature of 400 degrees Fahrenheit. There was a differentialpressure across the mat in the air draft ovens of 6 inches of water.Upon exiting the air draft ovens, each mat was feds between twostainless steel cylindrical rollers which compressed the thickness ofeach mat by approximately 50% into a sheet of nonwoven fabric with awidth of about 37 inches. Each 37-inch wide sheet of nonwoven fabric wascut into 6-inch wide strips 13, 15, 17, 19. The basis weight of eachsheet of nonwoven fabric was determined and to be in the range of 0.5 to1.2 ounces per square foot. As a quality assurance step, once the stripsof nonwoven fabric were cut, they were tested on a Frasier air flowtester to determine air permeability in cubic feet per minute per squarefoot. The strips of nonwoven fabric 13, 15, 17, 19 were then loaded ontothe roll support shafts 79 of the roll support 75, one roll at eachstage of the winding machine 71.

The specifications of the strips of nonwoven fabric 13, 15, 17, 19 wereinput into the data processing system. The hollow mandrel 47 was made ofstainless steel and had a nominal outside diameter of 1 inch. The heattransfer medium pumping device was started and began pumping the heattransfer medium through the hollow mandrel 47 at varying flow rates suchthat the temperature of the annular exterior surface 49 of the hollowmandrel 47 was maintained at 200 degrees Fahrenheit. A first-stagecapstan driving motor was started at a control speed of approximately 50hertz. The first-stage heater array 63 was turned on and supplied with avoltage of electricity sufficient to create a temperature at the hollowmandrel 47 of 300 degrees Fahrenheit.

The first band 14 of nonwoven fabric strip 13 was initiated by feedingthe nonwoven fabric strip 13 between the hollow mandrel 47 and thefirst-stage compression belt 55. The nonwoven fabric strip 13 washelically wound in an overlapping fashion upon itself forming band 14 asit was driven under the compression belt 55 and along the hollow mandrel47. As the outside diameter of band 14 increased, the driven capstan 106moved toward the driving capstan 105 so as to shorten the distancetherebetween and maintain a pressure of 10 pounds per square inchexerted on band 14 from compressed belt 55. This compression pressurewas a result of the tension in the compression belt 55 which wasdeveloped by the pressure in the tensioner air cylinder 133 of 50 poundsper square inch gage. The movement of the driven capstan 106 wasaccomplished by altering the pressure in the tensioner air cylinder 133.The digital linear encoder 117 detected the movement of the drivencapstan 106 and the appropriate modifications to the speed of thecapstan driving motor was made, if necessary. The temperature created bythe infrared heater 63 was the “ironing point” temperature. This ironingpoint temperature of 300 degrees Fahrenheit assisted compression andbonding of the base fibers between the layers of band 14. Under thissimultaneous application of heat and compression, the thickness of thestrips of nonwoven fabric 13 was compressed by approximately 50% andthere existed interlayer bonding.

The band 14 was allowed to travel through each stage of the windingmachine 71 and prior to encountering the compression belt at each stage,the capstan driving motor at that stage was turned on and set to thespeed of the first-stage capstan driving motor.

Once the band 14 progressed through all stages of the winding machine71, the second band 16 of nonwoven fabric strip 15 was initiated byfeeding the nonwoven fabric 15 between the second-stage compression belt57 and the annular exterior surface of band 14. The nonwoven fabric 15was helically wound in an overlapping fashion upon itself forming band16 as it was driven under compression belt 57 and along the hollowmandrel 47. The second-stage heater array 65 was turned on and suppliedwith a voltage of electricity sufficient to maintain an ironing pointtemperature of 300 degrees Fahrenheit at the annular exterior surface ofband 16. As the outside diameter of band 16 increased, the second-stagedriven capstan moved toward the second-stage driving capstan so as toshorten the distance therebetween and maintain a pressure of 10 poundsper square inch exerted on band 16 from compression belt 57. Thiscompression pressure was a result of the tension in the compression belt57 which was developed by the pressure in the second-stage tensioner aircylinder of 50 pounds per square inch gage. The movement of thesecond-stage driven capstan was accomplished by altering the pressure inthe second-stage tensioner air cylinder. The second-stage digital linearencoder detected the movement of the second-stage driven capstan and theappropriate modifications to the speed of the second-stage capstandriving motor was made, if necessary, to synchronize the speed of thesecond-stage capstan driving motor with the first-stage capstan drivingmotor. The ironing point temperature of 300 degrees Fahrenheit assistedcompression and bonding of the base fibers between the layers of band16. Under this simultaneous application of heat and compression, thethickness of the nonwoven fabric strip 15 was compressed byapproximately 50% and there existed interlayer bonding. The annularinterior surface of band 16 was bonded to the annular exterior surfaceof band 14 and band 16 progressed along the hollow mandrel 47 toward thethird-stage compression belt 59. The band 16 was allowed to travelthrough the remaining stages of the winding machine 71 and prior toencountering the compression belt at each stage, the capstan drivingmotor at that stage was turned on and set to the speed of thesecond-stage capstan driving motor.

Once the band 16 progressed through all the stages of the windingmachine 71, the third band 18 of nonwoven fabric 17 was initiated byfeeding the nonwoven fabric strip 17 between the third-stage compressionbelt 59 and the annular exterior surface of band 16. The nonwoven fabric17 was helically wound in an overlapping fashion upon itself formingband 18 as it was driven under compression belt 59 and along the hollowmandrel 47. The third-stage heater array 67 was turned on and suppliedwith a voltage of electricity sufficient to maintain an ironing pointtemperature of 300 degrees at the annular exterior surface of band 18.As the outside diameter of band 18 increased, the third-stage drivencapstan moved toward the third-stage driving capstan so as to shortenthe distance therebetween and maintain a pressure of 10 pounds persquare inch exerted on the band 18 from compression belt 59. Thiscompression pressure was a result of the tension in the compression belt59 which was developed by the pressure in the third-stage tensioner aircylinder of 50 pounds per square inch gage. The movement of thethird-stage driven capstan was accomplished by altering the pressure ofthe third-stage tensioner air cylinder. The third-stage digital linearencoder detected the movement of the third-stage driven capstan andappropriate modifications to the speed of the third-stage capstandriving motor was made, if necessary, to synchronize the speed of thethird-stage capstan driving motor with the first-stage capstan drivingmotor. The ironing point temperature of 300 degrees Fahrenheit assistedcompression and bonding of the base fibers between the layers of band18. Under this simultaneous application of heat and compression, thethickness of nonwoven fabric strip 17 was compressed by approximately50% and there existed interlayer bonding. The annular interior surfaceof band 18 was bonded to the annular exterior surface of band 16 andband 18 progressed along the hollow mandrel 47 toward the fourth stagecompression belt 61. The band 18 was allowed to travel through theremaining stage of the winding machine 71 and prior to encountering thefourth-stage compression belt, the fourth-stage capstan driving motorwas set to the speed of the third-stage capstan driving motor.

Once the band 18 progressed through all the remaining stage of thewinding machine 71, the fourth band 20 of nonwoven fabric strip 19 wasinitiated by feeding the nonwoven fabric strip 19 between thefourth-stage compression belt 61 and the annular exterior surface ofband 18. The nonwoven fabric strip 19 was helically wound in anoverlapping fashion upon itself forming band 20 as it was driven undercompression belt 61 and along the hollow mandrel 47. The fourth-stageheater array 68 was turned on and supplied with a voltage of electricitysufficient to maintain an ironing point temperature of 300 degrees atthe annular exterior surface of band 20. As the outside diameter of band20 increased, the fourth-stage driven capstan moved toward thefourth-stage driving capstan so as to shorten the distance therebetweenand maintain a pressure of 10 pounds per square inch exerted on the band20 from compression belt 61. This compression pressure was a result ofthe tension in the compression belt 61 which was developed by thepressure in the fourth-stage tensioner air cylinder of 50 pounds persquare inch gage. The movement of the fourth-stage driven capstan wasaccomplished by altering the pressure of the fourth-stage tensioner aircylinder. The fourth-stage digital linear encoder detected the movementof the fourth-stage driven capstan and appropriate modifications to thespeed of the fourth-stage capstan driving motor was made, if necessary,to synchronize the speed of the fourth-stage capstan driving motor withthe first-stage capstan driving motor. The ironing point temperature of300 degrees Fahrenheit assisted compression and bonding of the basefibers between the layers of band 20. Under this simultaneousapplication of heat and compression, the thickness of nonwoven fabricstrip 19 was compressed by approximately 50% and there existedinterlayer bonding. The annular interior surface of band 20 was bondedto the annular exterior surface of band 18 and band 20 progressed alongthe hollow mandrel 47 toward the measuring and cutting devices wherebyit was measured and cut to a length of 30 inches.

The resulting filter element 11 had a 1-inch nominal inside diameter, a2.5-inch nominal outside diameter and was cut to 30 inches long. Itweighed one pound and had an airflow capacity of 20 cubic feet perminute, producing a 4.9 inches of water column differential pressure.

In an alternate embodiment of the invention, an idler belt may beincluded at one or more stages of the multi-stage winding machine 71 soas to maintain the hollow mandrel 47 in a properly fixed position.

In another embodiment of the invention, a plurality of non-woven fabricstrips are added in a single stage of the multi-stage winding machine71.

It is noted that the process for making the filter element of thepresent invention, as described above, provides the filter element witha surface area that includes multiple overlapping layers of media (i.e.,bands) whereby adjacent layers have an intersection plane at the pointof joining. Such a design, in an embodiment, can enhance the filtrationcapacity of the bands. Moreover, with such a design, a gradient ofdensity within the filter element 11 can be provided across the depth ofthe filter element 11.

Before proceeding further, it may be useful to define some of the termsbeing used hereinafter. “Pore size” is an indication of the size of thepores in the media, which determines the size of particles unable topass through the media, i.e. micron rating. For most media, this may berelated as a distribution, since the pore size may not be uniformthroughout. “Permeability” is a measure of the resistance of the mediato flow. This can be measured in air or in a liquid. A higherpermeability means less resistance to flow and a lower pressure dropacross the media for a given flow. A lower permeability means moreresistance to flow or a high pressure drop across the media for a givenflow. “Fiber size” is a measure of the size of the fibers in the media.This is measured in microns, or for polymers, denier. Generally, thesmaller the fiber, the smaller the pores in the media. There isgenerally a distribution of fiber sizes which can change based upondesign. “Basis Weight” is how much the media weighs for a given surfacearea. This is generally measured in pounds (lbs.) per square yard, orgrams per square meter. “Porosity” (Void volume) is a measure of howmuch of the media volume is open space. Generally, a higher porosityindicates a higher dirt holding capability within the media and a higherpermeability.

As noted above, the material used and the method of manufacture caninfluence the characteristics of the media. To that end, thecharacteristics of the media can be utilized to develop a filter thatmay have a relatively significant filtration capacity. It is wellestablished that the three primary measures of filtration performance,that is, flow capacity, micron rating, and particle holding capacity,can be proportionately related to one another. For example, as themicron rating becomes tighter, the flow capacity tends to decrease.Likewise, as the micron rating becomes tighter, the particle holdingcapacity tends to decrease. Accordingly, based on these characteristics,a filter element can be designed, in accordance with an embodiment ofthe present invention, whose filtration capacity can provide the abilityto remove contaminant, while having relatively high particle holding andflow capacity, and the ability to maintain a specified micron rating.

With reference to another embodiment of the present invention, tofurther enhance the filtration capacity of filter element 11, thepresent invention may provide the filter element with an interlay ofmedia within at least one of bands 14, 16, 18 or 20. The presence ofsuch an interlay in the filter element 11 can, in an embodiment, providethe filter element 11 with additional surface area for filtration. Inparticular, to the extent that the interlay may be different incharacteristics and properties from the underlying filter element bands14, 16, 18 and 20, there can be a distinct and abrupt change in density,fiber size, etc., that, in effect, create additional surface area withinthe contiguous construction of a filter element of the presentinvention. This interlay can also create the ability to change directionof flow and to increase the deposition of specifically sizedcontaminants.

Looking now at FIG. 6A, there is illustrated a cross-sectional view of amulti-overlapped coreless filter element 60, in accordance with oneembodiment of the present invention. Filter element 60, as illustratedin FIG. 6A, may be manufactured using the process described above. Tothat end, similar to filter element 11, filter element 60 can includemultiple bands 61, 62, 63 and 64. Of course, additional or fewer bandsmay be provided should that be desired. Filter element 60 can furtherinclude an interlay 65 disposed within at least one over-lapping band,such as band 61. The presence of interlay 65 within overlapping band 61of filter element 60 can allow the filter element 60 to be designed insuch a way as to control and impart a particular filtration or flowpattern of the fluid moving within filter element 60, for instance, in asubstantially axially direction.

In accordance with an embodiment of the present invention, interlay 65may be made from a material or materials that can providecharacteristics different from those of the bands 61 to 64. In oneembodiment, these characteristics may be imparted based on the size of,for instance, the fibers, as well as the process or recipe used inmaking the interlay 65. In general, the fibers used can come indifferent diameters, typically micron (i.e., 1/1,000,000 meter) in size.The diameter may also be described in denier. A denier is the weight ingrams of 9,000 meters of the fiber. Using the density of, for instance,the polymer in the fiber, the diameter of the fiber can be calculatedfrom the denier. In an embodiment, the interlay 65 can be made up from amixture of fibers of widely different diameters. This mixture or recipecan determine the performance or characteristics of the interlay 65, anddepending of the application, the performance or characteristics ofinterlay 65 can be substantially different or slightly different thanthe characteristics or performance of bands 61 to 64.

Examples of materials that can be used in the manufacture of interlay 65can vary widely including metals, such as stainless steel, inorganiccomponents, like fiberglass or ceramic, organic cellulose, paper, ororganic polymers, such as polypropylene, polyester, nylon, etc., or acombination thereof. These materials have different chemical resistanceand other properties.

In addition, looking now at FIG. 6B, interlay 65, in one embodiment, maybe provided from a strip, such as strip 651, with a width substantiallysimilar in size to that of a strip, such as strip 611, being used inmaking the band within which the interlay 65 is disposed. Alternatively,the interlay 65 may be provided from a strip with a width measurablyless than the width of the strip used in the band within which theinterlay 65 is disposed. In an embodiment, the interlay 65 may include awidth approximately 2 inches less than the width of the strip used inthe band.

To dispose the interlay 65 in the manner illustrated in FIG. 6A, at thebeginning of the manufacturing process, strip 651 from which interlay 65is formed may be placed substantially parallel to and against a surfaceof, for example, strip 611 used in the formation of, for instance, band61. Strip 611, manufactured by the process indicated above, can benon-woven in nature. In an embodiment, the strip 651, which can also benon-woven or otherwise, may be placed against a surface of strip 611that subsequently can become an inner surface of band 61. Alternatively,strip 651 may be placed against a surface of strip 611 that subsequentlycan become an outer surface of band 61. Thereafter, as strip 611 iswound about mandrel 47 to form band 61, the strip 651 can be woundsimultaneously along with strip 611 of band 61 to provide theconfiguration shown in FIG. 6A. In other words, for example, each layerof the interlaying strip 651 may be sandwiched between two adjacentoverlapping layers of the non-woven strip 611. It should be noted thatthe interlay 65 within band 61 is provided above and below pathway 67formed by the mandrel 47 during the winding process, such as thatillustrated in FIG. 6A. Moreover, despite being illustrated inconnection only with band 61, it should be appreciated that interlay 65may be disposed within one or more of the remaining bands 62 to 64.Furthermore, each interlay 65 in each of bands 61 to 64, in anembodiment, may be provided with different or similar characteristics tothe other interlays, depending on the particular application orperformance desired.

In an alternate embodiment, as illustrated in FIG. 7, instead ofproviding interlay 65 within overlapping band 61, an interleaf 75 mayprovided circumferentially about overlapping band 71. To dispose theinterleaf 75 in the manner illustrated in FIG. 7, in one embodiment,subsequent to the formation of overlapping band 71, a strip, used in theformation of interleaf 75, may be wrapped or wound in an overlappingmanner similar to that for band 71 about an exterior surface of band 71to provide an overlapping profile exhibited by interleaf 75 in FIG. 7.Of course, although illustrated with only one interleaf, interleaf 75may be provided about one or more of the remaining bands in filterelement 70.

Alternatively, rather than providing an overlapping interleaf 75, aninterleaf 85, looking now at FIG. 8, may be disposed as one layer alongan entire length of filter element 80 and within band 81. In thisembodiment, strip 851 may be provided with a length substantiallysimilar to that of filter element 80 and a width substantially similarto a circumference of band 81. That way, band 81 of filter element 80may be positioned along the length of strip 851 and the width of strip851 subsequently wrapped once about band 81. This, of course, can bedone during the formation of band 81, so that interleaf 85 may beprovided within band 81, or after the formation of band 81, so thatinterleaf 85 may be provided about an exterior surface of band 81.Interleaf 85 may also be provided about one or more of the remainingbands in filter element 80.

In a related embodiment, strip 851 may be provided with a length shorterthan that of filter element 80. With a shorter length, interleaf 85 maybe provided about each band of filter element 80 and in a staggeredmanner from one band to the next (not shown).

In addition to the materials (e.g., types and sizes), thecharacteristics or properties of the interlay 65 as well as bands 61 to64, which may be referred to hereinafter as media, can be dependent onpore size, permeability, basis weight, and porosity (void volume) amongothers. The combination of these properties can provide the interlay 65,along with bands 61 to 64, with a particular flow capacity (differentialpressure of fluid across the filter), micron rating (the size of theparticles that will be removed from the filter element 60, particleholding capacity (the amount of contaminant that can be removed from theprocess by the filter element 60 before it becomes plugged), andphysico-chemical properties.

Moreover, by providing filter element 60 with interlay 65 havingdifferent characteristics and properties from those exhibited by themultiple overlapping bands 61 to 64, there can be, for example, adistinct and abrupt change in density within the filter element 60 that,in effect, can create additional surface area, thereby allowing for thegeneration of a gradient density within filter element 60 at a microlevel as well as a macro level.

The presence of interlay 65 within filter element 60 can also impart, inan embodiment, a substantially axial fluid flow pathway along the filterelement 60. Generally, the flow of fluid through the overlapping bands,for example, bands 61 to 64, is in a substantial radial direction acrossthe element 60 either from outside to inside or from inside to outside.However, using an interlay of more dense or less permeable media, asdescribed above, the flow of the fluid across filter element 60 can bedirected substantially axially along the length of the filter element60, as illustrated by arrow 66 in FIG. 6A.

A well established fact in filtration using depth media, such as filterelement 60, is the ability to remove particles that are relativelysmaller than the pore size. Very small particles in a gas, for instance,can move randomly in what has been described Brownian motion. Theseparticles can come in contact with fibers or liquid held in a filterelement, and may be removed even though, by their size, they can easilypass through the larger pores within bands of the filter element. Inaddition, particles in a fluid tend to have more mass than the fluidwithin which they are found. As a result, there is a tendency for theparticles to flow in a relatively straight line. Such a flow pattern cancreate an inertial impaction of the particles with a fiber, allow theparticles to stick to the fiber and be removed. Again, even though theseparticles may be small enough to pass through the pores of the filter,they are nevertheless removed.

Both of these removal mechanisms, in an embodiment, can likely increasefiltration capacity as the path along which the particles must travelthrough the filter element becomes more tortuous and/or longer. Inparticular, with a more tortuous and/or longer travel path, contactprobability by the particle can increase. Contact probability is theprobability that a particle will come in contact with a fiber or, in thecase that the fluid is a gas, come in contact with liquid held withinthe filter element, which allows its removal. Accordingly, by impartingaxial flow along the filter element, filter element 60 of the presentinvention can substantially increase its ability to remove relativelysmall particles while increasing its the flow capacity (i.e., removal ofmicron sized particles while providing larger particle holding and flowcapacity.)

For example, in a liquid filter element having an outside diameter (OD)of about 2.5″ and an inside diameter (ID) 1.19″, the radial depth of thefilter element may be about 0.655″. With such a filter element, aparticle or contaminant may typically flow radially approximately 0.665″in order to pass through this filter. On the other hand, when such afilter is provided with an interlay approximately 4.0″ in width, forinstance, interlay 65, within one band, such as band 61 in FIG. 6A, theparticle flowing through the filter element must now flow along adirection illustrated by arrow 66. Depending on where the particle comesinto contact with interlay 65, whether at point A or B or somewhere inbetween the particle may travel for approximately up to 4.665″ before itcan pass through the filter element. Such a distance is up to about 7.1times the distance without the interlay, thus, greatly increasing thecontact probability for removal of the contaminant. Of course, ifanother 4″ interlay were provided within a second band, the distancetraveled would be up to 8.665″ or 13.2 times that of a filter elementwithout an interlay.

Using the interlay 65 of the present invention, along with thecharacteristics that can be imparted to each of the bands 61 to 64, afilter element may be made whereby a specifically designed flow pattern(i.e., direction of fluid flow) can be imparted to a fluid movingthrough the filter element. In particular, between two extremes, if, forexample, the interlay 65 is substantially impermeable, then axial flowcan be mandated through the band within which the interlay 65 may bedisposed until the flow reaches an exit end of the band. If, on theother hand, the interlay 65 is substantially similar in characteristicsand properties to the band within which the interlay 65 may be disposed,then the flow through that band is likely to continue in a substantiallyradial direction through the interlay and band with little or no axialflow.

The ability of design a specific flow pattern across the filter elementdepends on finding a right balance and combination between the twoextremes described above. In an embodiment, the interlay 65 may bedesigned to be more dense and less permeable than the band within whichthe interlay is disposed. As such, when the fluid containing contaminantreaches the interlay 65, the direction of flow may either be through theinterlay or axially, depending on the content of the fluid. Thedirection of flow, in an embodiment, may be dictated by the pore size,permeability and other characteristics imparted to the band and theinterlay 65.

To the extent that the relatively dense interlay 65 may be permeable, inone embodiment, a cross flow filtration can be permitted through theinterlay 65. Specifically, as fluid flows along the interlay 65, thefluid may be permitted to flow across the permeable interlay 65, leavingthe contaminant behind. Over the life of the filter element, as therelatively dense interlay 65 becomes plugged with contaminants, fluidflowing along the interlay 65 may be forced to flow through an alternateflow path, e.g., in the direction of arrow 66 in FIG. 6A, through themore permeable band having greater void volume.

It should be appreciated that when using an interlay made with amaterial different than that used for the band within which the interlayis disposed, it may be possible to establish electrostatic charges dueto a physico-chemical interaction of the two different materials inclose proximity. The generation of electrostatic charges due to suchphysico-chemical interaction can lead to the manufacture of a filterelement containing a wide variety of fiber sizes. In addition, suchinteraction can lead to the manufacture of a diverse fiber matrix withdifferent fibers in different locations. Examples of fibers that may beemployed in the manufacture of the interlay and bands of the filterelement of the present invention include fine fibers, including thosefrom fiberglass, melt blown, or recent nano-fiber or nanoparticleadvancements.

To the extent that nanoparticles may be incorporated into the interlay65, such nanoparticles may be a waste adsorbent material capable ofremoving heavy metal contaminants, such as inorganic mercury (e.g.,divalent cation Hg²⁺, monovalent Hg₂ ²⁺, and neutral compounds such asHgCl₂, Hg[OH]₂,), organic mercury, such as methylmercury (e.g., CH₃HgCH₃ or CH₃ Hg⁺) as a result of enzymatic reaction in the sludge,metallic mercury, silver, lead, uranium, plutonium, neptunium,americium, cadmium and combinations thereof.

The waste adsorbent material, in an embodiment, may be a nanosorbentmaterial manufactured from self-assembled monolayers on mesoporoussupports (SAMMS). The support may be made from various porous materials,including silica. An example of a SAMMS material that can be used inconnection with the present invention includes thiol-SAMMS, such as thatdisclosed in U.S. Pat. No. 6,326,326, which patent is herebyincorporated herein by reference.

In accordance with one embodiment of the present invention, thenanosorbent material may be porous particles ranging from about 5microns to about 200 microns in size. In an embodiment, the particles,on average, may range from about 50 microns to about 80 microns in size,may include a pore size ranging from about 3 nanometers (nm) to about 4nm, and may be provided with an apparent density of ranging from about0.2 grams/milliliter to about 0.4 grams/milliliter.

The interlay design of the present invention, as noted above, may beused in connection with a filter element to treat contaminated fluid.Contaminated fluid that may be treated includes viscous fluid, such asoil, or non-viscous fluid, such as a liquid or a gas. In an applicationinvolving gas/liquid coalescence a challenge may arise involving removalof very fine aerosols, while maintaining the life of the coalescingelement over an extended period of time in the presence of solidcontaminants. It has been observed that by using an interlay design ofthe present invention, very fine aerosols can be captured in the finefibers of the interlay and can coalesce into droplets, which dropletseventually form a fluid flow down an axial path. The axial flow of thedroplets/fluid, in an embodiment, can increase the life of thecoalescing element by allowing some of the contaminants to be removed inthe drained liquids rather than remain caught in the interlay andsubsequently plugging it up. To a certain extent, this imparts aself-cleaning effect on the interlay, which can extend its life inservice.

In an alternate embodiment, an interlay that is less dense and more openthan the band within which it is disposed may also be used in anapplication involving gas/liquid coalescence. In such an embodiment, anarea within the coalescing element may be created where contaminants canbuild up and be deposited.

Moreover, it should be appreciated that when an interleaf, such asinterleaf 85, is designed to be substantially more dense and lessimpermeable than the band around which it is wrapped, fluid flowingthrough the filter element may be forced to move substantially along theentire length of the filter element, since the fluid may not be able totraverse across the dense interleaf.

While the invention has been described in connection with the specificembodiments thereof, it will be understood that it is capable of furthermodification. Furthermore, this application is intended to cover anyvariations, uses, or adaptations of the invention, including suchdepartures from the present disclosure as come within known or customarypractice in the art to which the invention pertains.

What is claimed is:
 1. A method of filtration comprising: a. introducing a fluid flow substantially radially into a filter element having an increasing gradient of density and an initial level of permeability, so as to remove certain particles from the fluid flow; b. allowing the radial fluid flow to encounter an area of decreased permeability at a predetermined depth within the filter element; c. redirecting the radial fluid flow to a substantially axial direction along a path of least resistance in the presence of pressure differential generated at the area of decreased permeability; d. allowing the fluid flow to continue moving in the substantially axial direction along the filter element; and e. allowing treated fluid to exit the filter element.
 2. A method as set forth in claim 1, wherein the step of redirecting further enhances removal of particles from the fluid flow.
 3. A method as set forth in claim 2, further including enhancing removal of the particles through the increased probability of inertial impaction or Brownian motion of particles in the fluid flow due to a longer fluid path through the filter element.
 4. A method as set forth in claim 1, wherein the gradient of density allows for an increased removal of the particles while increasing flow capacity of the filter element.
 5. A method as set forth in claim 1, further including reducing, over time, permeability of the filter element as additional particles get trapped therein, so that substantially all of the fluid flow eventually is forced to flow axially along the filter element.
 6. A method of claim 1 wherein in the step of allowing, the fluid flow is allowed to continue moving in an adjacent axial overlapping manner. 